If you are seeing a LED color on the device that is something other than blue / sky blue, you can refer to the device manual to see what the colors mean. 

The LED colors are more useful with devices that do not have a LCD screen.

The device manuals are included in the BioStar installation CD file.

Below are links to the download page

BioStar 1

BioStar 2

[BioEntry W Device Manual]

Below are the cause of some of the more common LED colors

Blue / Skyblue 

Device has received an IP address and is operating correctly.

Blue / Yellow

Case 1: Using ethernet connection and device is configured as master: 

This means that the device is having issues acquiring an IP address from the DHCP server.

Please check if your DHCP server is operating properly.

Case 2: Using RS485 connection and device is configured as slave: 

This means that the device is not connected with the master device with RS485. 

Check the RS-485 wiring and search the device with the master device to add it as slave. 

Refer to the link below to troubleshoot connection issues:
[BioStar 1] Connection Modes (Direct / Server)

[BioStar 2] Connection Modes and Troubleshooting Connection

Else you can try resetting the network settings or searching it with the instruction shown in the link below for ethernet related connection issues:
 How to Check Suprema Device’s IP & MAC Address Manually

Blue / Red

In this case the RTC (real-time clock) battery is discharged.

The result would be that the device time will be reset every time the device power is reset.

Note: If this is a new device that has been in the warehouse for a long time, the battery could have lost its charge. If you plug the device to the power, the battery should be charged again after a few hours. Please use the power adapter rather than POE at this point.

If this is an old device, the battery may not be charged again because it used all its cycle.

Hence it will remain in its LED color. In such case you will have to process the device as RMA.

Red / Red

If the device blinks red only, it usually means that the hardware is malfunctioning. 

This is usually resolved through hardware repair. 

Process the device through RMA. 

In cases of BioEntry Plus, try this solution first: [Known Issue] BioEntry Plus 1.x Blinking Red LED Issue